question_answer

If \[x=a{{\cos }^{3}}\theta ,y=a{{\sin }^{3}}\theta \], then \[\sqrt{1+{{\left( \frac{dy}{dx} \right)}^{2}}}=\] [EAMCET 1992]

A)            \[{{\tan }^{2}}\theta \]

B)            \[{{\sec }^{2}}\theta \]

C)            \[\sec \theta \]

D)            \[|\sec \theta |\]